My 406 runs quite well when cool,but I notice some power loss once it gets hot. I'm sure it's normal,especially in this heat,and I'm talking about after driving an hour. The engine temps stay in the 160-180 degree range,so I'm sure I'm not overheating. I was thinking of trying a phenolic spacer or something to try to insulate the carb from the intake.

Any thaughts on this.?Do they work?

 

phenolic spacer is better than aluminum, but not as good as wood.

I had gas boiling in the bowls when I would shut off the motor until I put 1/2 inch wood spacer from Jeg's I went with the open hole because i have a single plane.

 

Any time you keep heat from the carb or fuel you will gain HP. It makes for a denser mixture. The spacer itself will increase torque in MOST instances. Depends on intake design, carb, cam etc. It is something that you have to experiment with. Try it !!
Pops

 

A ported four hole spacer is the best{not a standard 4-hole, but hand ported}.
If the temps are the problem or concern...Use phenolic unless you can find a wooden one as stated.

 

Mine bioled the fuel too,but I only saw that happen once and it was hotter than h#%^*(ll that day.I may still try one just for grins.

 

funniy Phenolic is a dielectric, very low coefficient of expansion WOOD based plastic.
what type of intake do you have? Dual or single plane? Id try a RPM air gap. It might help you out. Nothing wrong with water/meth injection either.

 

I swapped the RPM for the Vic Jr in an effort to bleed off some low end torque. Transmission life was short,and traction was non existant on a hard launch.The jury's still out on the swap,but I gotta say I love the 7000 rpm sound the solid cam and Vic Jr has.

Not sure how thick a spacer will fit under the hood. I'm guessing only a half inch. I tried my Vic Jr with a 4" element instead of the 3" and there was witness marks on the hood,so I'm sure it's less than an inch.

 

Do you have cool air going to your carb? yo might wanna consider one of those ram air boxes that fit on the carb, they are always advertising in the back of HOTROD, PHR, etc.
I know this sounds out of the ordinary but if you have cold air ducted from the front of the car, it opens the possibility if using a CO2 intercooler kit to freeze the ebottom of the intake for an extra 10-20 hp. This will only work if you have the ducting in place , as it will prevent the motor from breathing the inert gas ('cause that sure wont make power!lol) they sell the kits in jegs under the sport compact page. They other totally bitchin side effect of this system is that you now also have a very effective on board fire control system.

 

Your never going to convince me that air gap manifolds cool the incoming A/F charge.

Just for grins I was looking around under my hood with one of those thermal temp guns. My motor was hot and up to temp after driving it. With the motor running. The "Air Gap" single plane four leg intake tubes were nearly identical temp from right next to the head all the way to my wood spacer.

Aluminum is one of the better heat conducters know to man.

The second BS hype about air gap is heat exchange is not instant. How long does it take for a molocule of air passing over your throttle blade to pass 8 inches to head intake port at 6000 rpm when each cylinder is firing 3000 times per minute? That's firing 50 times per second. Just a rough estimate. The intake cycle at 6000 rpm is @.005 seconds. How much heat is the air fuel mix going to gain in 5 one thousands of one second.

Really who cares how much time it spends in the intake track if the air gap is not cooler than a conventional intake. I don't have any magic wind blowing there or radiant cooling fins on the legs.

You have to have some filters on your head to filter out sales B.S.

 

I think the design had mre to do with the fact that guys like me ice the intake down between runs. This style intake make it far easier (and cleaner) to do. Having a little space between the runners and hot crankcase oil can stave off heat soak a little longer.
True, were talking about a percent of two but like I said I think they had the street strip guys in mind. Perhaps in the right chassis there would be sufficient airflow to cool the intake some, but never be cooler than the ambient air. It's more about heating the intake charge LESS than a conventional dual plane
But the benefits of a iced intake are irrefutible, a tenth or more usually. want evidence? look at nearly all current Oem intakes. They are plastic, and not so much for production savings (in fact Dupont Zytel isn't cheap at all) but for the fact that they have a very low thermal conductivity. A win win for them, more power, less hydrocarbons, and lower combustion temps resulting in less oxides of nitrogen.

 

It will lose some torque and the fuel will get a cooler charge.

 

just some tuning wisdom i picked up a while ago.

my 427 big block corvette had a 160 thermostat in it and boat loads of timing (my fathers thought this was a good thing... silly him) and it had a huge amount of grunt but had hot start problems and pinging problems when it got hot on the highway. and the power was very inconsistant with wandering engine and ambient air temps. this seems like what your describing.

i switched to a 195 thermostat and droped about 10 degrees of timing (im back to stock 4 degrees base) and the engine runs rougher cold but once it gets hot it has more ***** than ever. especially up top. and i can beat on it and beat on it without ever skipping a beat. and the power output is far more consistant with a constant engine temp.

and its easyer to tune a engine that is always at the same temp. espeically with old technology distributors and carburators.

so if your temp is wandering 20+ degrees putting in a 195 thermostat will make your engine easyer to tune and more consistant. you just gotta re-tune for the hotter engine.

alot of people get uncomfortable with the idea of their "performance" engine running around 200 degrees. but get over it. 200 isnt overheating. pretty much its not overheating untill 240 or so. and i flog my car on hot days on the highway up to about 220 degrees. at which point i cant get it any hotter. and it absolutely loves it.

and yea cold air is a good thing if you can get it to the carb.

 

How would you know if the fuel is boiling over? Does it disapper completely? How should I check it?

 

You can hear it purculating like an old coffee pot.I ended up with only a 1/2" wood spacer and haven't run it yet so I can't say weather or not it makes a difference.Hood clearance is now only 3/8"

 

The insulating carb spacer will work to keep the carb cool as long as the engine compartment is kept reasonably cool.

As far as overall power loss from intake heating, the carb is the least of your worries. It is the temperature of the heads and intake runners that end up radiating heat into the intake charge. Run the hell out of your engine, then stop and whip open the hood. Grab one of the intake runners. If you can hold on for a little while you are good to go. If you can't then you need to insulate the bottom of the manifold, or lower the heat coming from the heads and engine.

 

They do work but.......
Do you have steel or alum heads
Mech or electric fuel pump
What size/type fuel line front to rear
I have used a NASCAR style fuel pump insulator set-up that also uses a spacer.......It keeps the hot oil off the pump & isolates the pump body from the block. Between that 1/2 fuel line and the carb spacer my little 331 likes it a lot
Cool air and a warm engine are best for any gen1 to LS7

 

All Throttle: Where did you get your fuel pump insulator? I tried to get one and all I got was referred to retailers in Bakersfield and LA. Nobody knew what I was talking about. I remember a forum member saying that he had checked this out and it was effective at reducing fuel temps 40o. That would make a diff on a hot day I would think? Cool fuel + reduced under hood temps = power, unless it's winter and my AG is too cold. lol

Rick

 

Rick,
I knew I posted on this before...........search is a great thing

http://forums.corvetteforum.com/show...um_id=7&arch=1